The present invention concerns locks of the axial pin tumbler type. This form of lock is well known in the art as exemplified by U.S. Pat. Nos. 3,261,188 and 3,258,945. A barrel lock derives its name from the fact that it includes a barrel-like structure disposed within a housing. Typically, the barrel is employed in vending machines and coin operated vending machines. The actuating element often consists of a pivoted lever or latch which toggles between unlocked and locked positions when rotated through a short arc. In the case of coin operated bulk vending machines, the actuating element is a threaded connection between the barrel lock, itself, and a threaded rod.
Referring to U.S. Pat. No. 3,258,945, it describes a conventional barrel lock where the combination, defined by axial pins, can be changed. The patent describes a removable pilot shaft, the position of which is fixed relative to the housing due to the cooperation of a positioning lug in the housing wall and a mating groove on the pilot shaft. With respect to changing the barrel lock combination, it exemplifies the prior art, i.e. the requirement to completely disassemble the tumblers once the pilot shaft is removed to reset the combination.
Often for security reasons, there is a need to change the lock combination of a barrel lock, and in some instances, changing the combination on a regular basis is a matter of management policy. A barrel lock combination is changed by disassembling the lock and replacing the tumblers. The new installed tumbler arrangement has different tumbler pin pairs (split pins) of different lengths and the new split pin tumbler combination provides an assembly having a different pin depth configuration. Accordingly, a new key corresponding to the new depth configuration is required.
Tumbler conversion of conventional barrel locks have the following principal disadvantages. The conversion of the lock combination is complicated, time consuming and troublesome in that a large number of delicate parts must be disassembled, removed and reassembled. Typically, there are many split pin tumblers (four to seven) where each tumbler comprises two pins and a small spring. These pins and springs are small and difficult to manipulate. Consequently, care and accuracy must be exercised to install the tumbler components in their proper plan location according to the new combination to correspond with the new key. In other words, to change the combination, accurate matching of each pin of the upper pin set with its mating pin of the lower set and placement in the barrel lock is required.
Clearly, the great number of small parts greatly increases the likelihood of mishandling and loss. Furthermore, in most assemblies, a number of other parts must also be removed even before achieving access to the tumbler assembly. Thus, yet more parts must be removed, accounted for and replaced.
Another disadvantage related to changing the combination is the need for careful stockpiling of parts (new tumbler sets and corresponding keys). This is inconvenient and increases cost in that the new pins must be ordered, purchased and inventoried. Consequently, not only are part costs increased but also labor costs.
In terms of a functional disadvantage, only the depth-wise configuration of the tumbler assembly can be modified in conventional barrel locks. The planar configuration remains the same.